Transfer of Metals Relevant to the Nuclear Fuel Cycle into Lumbriculus variegatus from Boreal Freshwater Sediments

Abstract

Radioecological modeling requires information about the transfer of different elements and their radionuclides. These models have traditionally used radionuclide concentrations in water to predict concentrations in aquatic organisms. In addition, these models often assume this accumulation to be linear. In this study, we investigated the transfer of Ba, Co, Ni, Sr, U, and Zn from sediment and artificial freshwater to laboratory-reared benthic Oligochaeta (Lumbriculus variegatus). Total elemental concentrations were used as substitute measurements for specific radionuclides. The radioactive isotopes of these metals are an important part of the nuclear fuel cycle. During various parts of this cycle, they can end up in aquatic environments, mostly at low concentrations. Sediment samples were collected from three small lakes connected to a former uranium mine in Eastern Finland, as well as from a reference lake from a different drainage area nearby. A 28-day bioaccumulation experiment was conducted using collected samples and artificial freshwater. Concentrations measured from sediment, porewater, overlying water, and L. variegatus indicated importance of sediment as a source of uptake for all tested metals. Linear accumulation assumption (constant concentration ratio) also did not appear to be correct for most metals. Metal uptake by L. variegatus seemed to reduce at higher sediment concentrations for most metals, except for Ba and Co. Thus, the common assumptions related to radioecological modeling were not supported by our findings for majority of tested metals and accumulation sources. Further basic research is required to develop more accurate and robust radioecological models.